1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to an LCD capable of reducing crosstalk between pixels without degrading the quality of two-dimensional (2D) images shown on the LCD screen.
2. Description of the Prior Art
With a development of three-dimensional (3D) technology, people have more interest in seeing 3D movies by wearing 3D display devices. FIG. 1 shows a cross-section view of a common 3D LCD glasses. The 3D LCD comprises a thin film transistor-liquid crystal display (TFT-LCD) module 110 and a phase retarder 120. The TFT-LCD module 110 comprises a TFT substrate 111. A color filter (CF) substrate 130 is disposed between the TFT-LCD module 110 and the phase retarder 120. A transparent TFT circuit is disposed on the TFT substrate 111. The CF substrate 130 comprises multiple colorful green units constituting the three primary colors, red, green, and blue (RGB). Pixel signals on the 3D LCD panel form a cycle of a right-eye signal and a left-eye signal from top to bottom. In this way, a ray signal displayed on the display device can be received into the human eye in a method of horizontal stripes interweaved at intervals, as shown in FIG. 2.
The phase retarder 120 is fixed in front of the TFT-LCD module 110. The right eye and the left eye obtain different phase compensation values through a phase arrangement of the phase retarder 120 depending on the cycle of the right-eye and left-eye signals from top to bottom which is formed by the pixel signals, causing the right-eye and left-eye signals having the same vertical polarization output by the TFT-LCD module 110 to be transformed into the right-eye and left-eye signals having different polarized light. As shown in FIG. 1, if the TFT-LCD module 110 outputs vertically polarized right-eye and left-eye signals, the right-eye pixel signal becomes horizontally polarized after passing through a half-wave plate while the left-eye pixel signal remains vertically polarized after passing through a zero-wave plate. Further, the right-eye and left-eye signals can be distinguished with a pair of polarized glasses.
However, this design has a defect as shown in FIG. 1. The defect is that, there is a limit to observation at a large vertical viewing angle. The viewing angle cannot exceed ±θ1. Once the viewing angle exceeds ±θ1, the left-eye pixel signal transmits the half-wave plate and the right-eye pixel signal transmits the zero-wave plate. Thus, in addition to the left-eye signal detected through a left-eye vertical polarizer, the vertical right-eye signal is detected after the right-eye pixel signal at the large viewing angle passes through the zero-wave plate. And in addition to the right-eye signal detected through a right-eye horizontal polarizer, the horizontal left-eye signal is detected after the left-eye pixel signal at the large viewing angle passes through the half-wave plate. Accordingly, crosstalk occurs; that is, a dragging phenomenon is generated in a high contrast screen.
As shown in FIG. 3, another method of reducing crosstalk between pixels in the LCD is designing a black matrix on the CF substrate 130. A diameter a of the half-wave plate and of the zero-wave plate can be shortened to a usable diameter b. Thus, the angle of the right-eye and left-eye signals at a large viewing angle increases through the corresponding phase retarder 120, thereby increasing a viewing angle without generating crosstalk. However, the black matrix on the CF substrate 130 causes the brightness of 2D images shown on the LCD screen to decrease when a viewer views the 2D images.
As shown in FIGS. 4 and 5, another method of reducing crosstalk between pixels in the LCD is changing the illumination scope of pixels. The details are as follows: two data lines or two scan lines are used to control grayscale signal and black image signal of the pixel signals independently, so that the grayscale signal and the black image signal can be shown at intervals. Since the pixel signals output by the TFT-LCD module 110 have the black image signal, the duration of viewing the right-eye signal or the left-eye signal at a large viewing angle increases, reducing crosstalk between the adjacent pixels.
But the above-mentioned method has two defects: the cost of driver chips suffers the increase because double data lines or scan lines are used; the method is not suitable for the charging sharing (CS) model in which a main sub-pixel area is distinguished from a sub-pixel area through the charge and discharge of a capacitor. As shown in FIG. 6, a main sub-pixel 620 and a secondary sub-pixel 630 are connected to different pixel capacitors (not shown), so voltage applied to the main sub-pixel 620 and to the secondary sub-pixel 630 is determined differently in the CS mode. Under the condition of a fixed pixel capacitor, the main sub-pixel 620 and the secondary sub-pixel 630 form a specific relation between the voltages across them. When the pixel is on a high-level grayscale, the main sub-pixel 620 shows a primary grayscale signal and the secondary sub-pixel 630 shows a secondary grayscale signal (there is a ratio between the secondary grayscale signal and the primary grayscale signal). The secondary sub-pixel 630, instead of keeping black, becomes brighter, which hinders a real black image signal from being generated when the LCD shows 3D images.
As such, it is a considerable need for an LCD to resolve the above-mentioned problems.